Bandpass Directional Couplers with Electromagnetically-Coupled Resonators

Compact 90- and 180-degree directional couplers incorporating bandpass characteristics are presented. They can integrate a bandpass filter and a power-divider/combiner in an RF transceiver, resulting in its miniaturization. The bandpass directional coupler can be represented as a coupled-resonator network, and its coupling coefficients and external-Q can be determined from a desired coupling ratio and operational bandwidth of the bandpass coupler. Measured results are also presented on a Ku-band bandpass 180-degree directional coupler with TE _01delta-mode dielectric resonators